ANU Research Publications

Permanent URI for this collectionhttps://hdl.handle.net/1885/26

The Australian National University's Research Publications collection is an online location for collecting, preserving and disseminating the scholarly output of the University. This service allows members of the University to share their research with the wider community. ANU Open Research accepts journal articles, conference papers, book chapters, working or technical papers and other forms of scholarly communication.

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Now showing 1 - 20 of 133072

Open Access
Hate Speech and Atrocity Prevention in Asia: Patterns, Trends and Strategies
(Brill - Nijhoff, 2023) Jacob, Cecilia; Morada, Noel
This article introduces the conceptual and analytical framework for this special issue on hate speech and atrocity prevention in Asia. It defines hate speech and incitement, and explains the process and context through which hate speech and incitement operates as a risk factor for atrocities. It also provides an explanation of the international legal framework regulating hate speech and incitement that informs the approach of the articles in this issue.
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Testing core creation in hydrodynamical simulations using the HI kinematics of field dwarfs
(EDP Sciences, 2017) Papastergis, E.; Ponomareva, Anastasia
Process that is attributed to star formation-related baryonic feedback. Core creation is regarded as one of the most promising solutions to potential issues faced by lambda cold dark matter (Lambda CDM) cosmology on small scales. For example, the reduced dynamical mass enclosed by cores can explain the low rotational velocities measured for nearby dwarf galaxies, thus possibly lifting the seeming contradiction with the Lambda CDM expectations(the so-called "too big to fail" problem). Here we test core creation as a solution of cosmological issues by using a sample of dwarfs with measurements of their atomic hydrogen (HI) kinematics extending to large radii. Using the NIHAO hydrodynamical simulation as an example, we show that core creation can successfully reproduce the kinematics of dwarfs with small kinematic radii,R less than or similar to 1.5 kpc. However, the agreement with observations becomes poor once galaxies with kinematic measurements extending beyond the core region, R approximate to 1.5-4 kpc, are considered. This result illustrates the importance of testing the predictions of hydrodynamical simulations that are relevant for cosmology against a broad range of observational samples. We would like to stress that our result is valid only under the following set of assumptions: i) that our sample of dwarfs with HI kinematics is representative of the overall population of field dwarfs; ii) that there are no severe measurement biases in the observational parameters of our HI dwarfs (e.g., related to inclination estimates); and iii) that the HI velocity fields of dwarfs are regular enough to allow the recovery of the true enclosed dynamical mass.
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Neutrinos from type Ia supernovae: The gravitationally confined detonation scenario
(American Physical Society, 2017) Wright, Warren P.; Kneller, James P.; Ohlmann, Sebastian T..; Röpke, F K; Scholberg, Kate; Seitenzahl, Ivo
Despite their use as cosmological distance indicators and their importance in the chemical evolution of galaxies, the unequivocal identification of the progenitor systems and explosion mechanismof normal type Ia supernovae (SNe Ia) remains elusive. The leading hypothesis is that such a supernova is a thermonuclear explosion of a carbon-oxygen white dwarf, but the exact explosion mechanism is still a matter of debate. Observation of a galactic SN Ia would be of immense value in answering the many open questions related to these events. One potentially useful source of information about the explosion mechanism and progenitor is the neutrino signal because the neutrinos fromthe different mechanisms possess distinct spectra as a function of time and energy. In this paper, we compute the expected neutrino signal from a gravitationally confined detonation (GCD) explosion scenario for a SN Ia and show how the flux at Earth contains features in time and energy unique to this scenario. We then calculate the expected event rates in the Super-K, Hyper-K, JUNO, DUNE, and IceCube detectors and find both Hyper-K and IceCube will see a fewevents for aGCDsupernova at 1 kpc or closer, while Super-K, JUNO, and DUNE will see events if the supernova is closer than similar to 0.3 kpc. The distance and detector criteria needed to resolve the time and spectral features arising from the explosion mechanism, neutrino production, and neutrino oscillation processes are also discussed. The neutrino signal fromthe GCD is then compared with the signal froma deflagration-to-detonation transition (DDT) explosion model computed previously. We find the overall event rate is the most discriminating feature between the two scenarios followed by the event rate time structure. Using the event rate in the Hyper-K detector alone, the DDTcan be distinguished fromtheGCDat 2 sigma if the distance to the supernova is less than 2.3 kpc for a normal mass ordering and 3.6 kpc for an inverted ordering.
Open Access
'Kill Two Million of Them': Institutionalised Hate Speech, Impunity and 21st Century Atrocities in India
(Brill - Nijhoff, 2023) Jacob, Cecilia; Kanth, Mujeeb
Hate speech and incitement have been instrumental in atrocity crimes that have occurred in India, even prior to its independence. These atrocities include targeted killings of minorities based on religious and ethnic identity, and demonstrate persistent features of systematic, orchestrated violence that is fuelled by a Hindu nationalist ideology. This ideology is routinely promulgated at the highest levels of political leadership. This article traces both the historical and institutional character of hate speech and incitement in India to understand its repeated manifestation over time. Through case studies of recent violence, it considers the implications of new legal developments, technology and the covid-19 pandemic on the character and dynamic of hate speech, incitement and atrocity violence in India. It considers key reforms and areas for accountability on which the international community could engage the government and civil society in India on the issue of hate speech and incitement to promote atrocity prevention at the domestic level.
Open Access
Characterising spatiotemporal variability of South Asia?s climate extremes in past decades
(Inter-Research, 2019) Chen, Yun; Xu, Tingbao; Shui, Junfeng; Liu, Rui; Wahid, Shahriar; Shi, Kaifang; Yang, Haichang; Cheng, Zhibo
We systematically examined past spatiotemporal changes in climate variability to gain some cross-regional insights into South Asia’s vulnerability to extreme conditions. Gridded Asian Precipitation-Highly-Resolved Observational Data Integration Towards Evaluation (APHRODITE) precipitation and Princeton Global Meteorological Forcing Dataset (PRINCETON) temperature data from 1975−2004 were used to derive a suite of annual extreme indices. Longterm mean and decadal variations of these indices were mapped. Long-term change tendencies were also detected from a suite of ‘slope’ maps composed by the 30 yr change trend at each grid cell in the region. Most precipitation indices indicated a tendency towards drier conditions, whereas all temperature indices marked a steady coherent warming trend. The extremely wet day precipitation index exhibited the largest change, indicating an increase in heavy precipitation in South Asia. The highest maximum temperature extreme showed increases, indicating more unbearable heatwaves in the region. These trends present a previously unrecognised regional picture of the patterns and trends in historical climate extremes, with each grid cell representing spatiotemporal characteristics of changes. The present study is superior to most studies that only summarise an averaged regional trend from tendencies over large areas, and therefore will improve trans-boundary understanding of extreme climates in South Asia. Our study also exemplifies the application of existing gridded regional/global data sets. It provides valuable means of cross-regional information for bridging gaps where gauging observations are unavailable, particularly in data-poor developing countries.
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Wallaby Early Science - IV. ASKAP H I imaging of the nearby galaxy IC 5201
(Oxford University Press, 2019) Kleiner, D.; Koribalski, Baerbel S.; Serra, P.; Whiting, M. T.; Westmeier, T.; Wong, O.I.; Kamphuis, P.; Popping, A.; Bekiaris, G.; Elagali, A.; Shao, Li
We present a Wide-field ASKAP L-Band Legacy All-sky Blind surveY (WALLABY) study of the nearby (vsys = 915 km s−1) spiral galaxy IC 5201 using the Australian Square Kilometre Array Pathfinder (ASKAP). IC 5201 is a blue, barred spiral galaxy that follows the known scaling relations between stellar mass, SFR, H i mass, and diameter. We create a four-beam mosaicked H i image cube from 175 h of observations made with a 12-antenna sub-array. The root mean square noise level of the cube is 1.7 mJy beam−1 per channel, equivalent to a column density of = 1.4 × 1020 cm−2 over 25 km s−1. We report nine extragalactic H i detections – five new H i detections including the first velocity measurements for two galaxies. These sources are IC 5201, three dwarf satellite galaxies, two galaxies, and a tidal feature belonging to the NGC 7232/3 triplet and two potential infalling galaxies to the triplet. There is evidence of a previous tidal interaction between IC 5201 and the irregular satellite AM 2220−460. A close fly-by is likely responsible for the asymmetric optical morphology of IC 5201 and warping its disc, resulting in the irregular morphology of AM 2220−460. We quantify the H i kinematics of IC 5201, presenting its rotation curve as well as showing that the warp starts at 14 kpc along the major axis, increasing as a function of radius with a maximum difference in position angle of 20°. There is no evidence of stripped H i, triggered or quenched star formation in the system as measured using DECam optical and GALEX UV photometry.
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The Quadratic Programming Method for Extracting Emission Line Maps from Line-blended Narrowband Images
(Institute of Physics Publishing, 2019) Ueta, T.; Mito, Hiroyuki; Otsuka, Masaaki; Nakada, Y.; Conn, Blair; Ladjal, Djazia
We present a method to separate blended line emission from a set of narrowband (NB) images whose distinct throughput profiles overlap with each other. This method, based on the principle of quadratic programming (QP), treats line blending as a linearly constrained quadratic optimization problem and finds the solution by imposing a condition that the desired individual line intensities are always positive while allowing measurement uncertainties. We demonstrate the method for the quintessential example of line blending in the Hα complex by the Hα and [N ii] lines using the archived Hubble Space Telescope WFPC2 and WFC3 NB images of the planetary nebula NGC 6720, in comparison with its genuine line maps extracted from a spectral cube obtained by our own long-slit scan mapping observations with the Gemini Multi-Object Spectrograph at Gemini-North. Such line-blended NB images typically permit only qualitative line diagnostics, which can lead to a factor of a few difference in the line flux ratios. This novel QP method, however, can extract individual line emission maps as long as the number of line-blended but well-calibrated NB images of differing throughputs is equal to or grater than the number of emission line maps to be extracted. The proposed QP method provides a viable alternative to the existing line emission calibration methods: a simple but innovative way to enable quantitative fully 2D plasma diagnostics at the pixel scale of input NB images available from various instruments, telescopes, and archives.
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Star-forming, rotating spheroidal galaxies in the GAMA and SAMI surveys
(Oxford University Press, 2019) Moffett, Amanda J.; Phillipps, Steven; Robotham, A. S. G.; Driver, Simon; Bremer, Malcom N.; Cortese, L; Wong, Oiwei Ivy; Brough, Sarah; Brown, Michael J I; Bryant, J. J.; Medling, Anne
The Galaxy And Mass Assembly (GAMA) survey has morphologically identified a class of 'Little Blue Spheroid' (LBS) galaxies whose relationship to other classes of galaxies we now examine in detail. Considering a sample of 868 LBSs, we find that such galaxies display similar but not identical colours, specific star formation rates, stellar population ages, massto- light ratios, and metallicities to Sd-Irr galaxies. We also find that LBSs typically occupy environments of even lower density than those of Sd-Irr galaxies, where ∼65 per cent of LBS galaxies live in isolation. Using deep, high-resolution imaging from VST KiDS and the new Bayesian, 2D galaxy profile modelling code PROFIT, we further examine the detailed structure of LBSs and find that their Sérsic indices, sizes, and axial ratios are compatible with those of low-mass elliptical galaxies. We then examine SAMI Galaxy survey integral field emission line kinematics for a subset of 62 LBSs and find that the majority (42) of these galaxies display ordered rotation with the remainder displaying disturbed/non-ordered dynamics. Finally, we consider potential evolutionary scenarios for a population with this unusual combination of properties, concluding that LBSs are likely formed by a mixture of merger and accretion processes still recently active in low-redshift dwarf populations.We also infer that if LBS-like galaxies were subjected to quenching in a rich environment, they would plausibly resemble cluster dwarf ellipticals.
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The presence of interstellar scintillation in the 15 GHz interday variability of 1158 OVRO-monitored blazars
(Oxford University Press on behalf of the Royal Astronomical Society, 2019-11-11) Koay, J. Y.; Jauncey, David; Hovatta, T.; Kiehlmann, S.; Bignall, Hayley E; Max-Moerbeck, W.; Pearson, T. J.; Readhead, A. C. S.; Reeves, R.; Reynolds, Cormac; Vedantham, H.
We have conducted the first systematic search for interday variability in a large sample of extragalactic radio sources at 15 GHz. From the sample of 1158 radio-selected blazars monitored over an ∼10 yr span by the Owens Valley Radio Observatory 40-m telescope, we identified 20 sources exhibiting significant flux density variations on 4-d time-scales. The sky distribution of the variable sources is strongly dependent on the line-of-sight Galactic H α intensities from the Wisconsin H α Mapper Survey, demonstrating the contribution of interstellar scintillation (ISS) to their interday variability. 21 per cent of sources observed through sightlines with H α intensities larger than 10 rayleighs exhibit significant ISS persistent over the ∼10 yr period. The fraction of scintillators is potentially larger when considering less significant variables missed by our selection criteria, due to ISS intermittency. This study demonstrates that ISS is still important at 15 GHz, particularly through strongly scattered sightlines of the Galaxy. Of the 20 most significant variables, 11 are observed through the Orion–Eridanus superbubble, photoionized by hot stars of the Orion OB1 association. The high-energy neutrino source TXS 0506+056 is observed through this region, so ISS must be considered in any interpretation of its short-term radio variability. J0616−1041 appears to exhibit large ∼20 per cent interday flux density variations, comparable in magnitude to that of the very rare class of extreme, intrahour scintillators that includes PKS0405−385, J1819+3845, and PKS1257−326; this needs to be confirmed by higher cadence follow-up observations.
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Detection statistics of the RadioAstron AGN survey
(Pergamon-Elsevier Ltd, 2020) Kovalev, Y. Y.; Kardashev, N. S.; Sokolovsky, Kirill V.; Voitsik, P. A.; Anderson, J. M.; Andrianov, A. S.; Avdeev, V. Yu.; Bartel, N.; Bignall, Hayley E.; Burgin, M. S.; Jauncey, David
The largest Key Science Program of the RadioAstron space VLBI mission is a survey of active galactic nuclei (AGN). The main goal of the survey is to measure and study the brightness of AGN cores in order to better understand the physics of their emission while taking interstellar scattering into consideration. In this paper we present detection statistics for observations on ground-space baselines of a complete sample of radio-strong AGN at the wavelengths of 18, 6, and 1.3 cm. Two-thirds of them are indeed detected by RadioAstron and are found to contain extremely compact, tens to hundreds of las structures within their cores.
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Around the world with Space VLBI: A sense of many places
(Pergamon-Elsevier Ltd, 2020) Jauncey, David
Open Access
Long-term spatio-temporal precipitation variations in China with precipitation surface interpolated by ANUSPLIN
(Nature Publishing Group, 2020) Guo, Binbin; Zhang, Jing; Meng, Xianyong; Xu, Tingbao; Song, Yongyu
Climate changes significantly impact environmental and hydrological processes. Precipitation is one of the most significant climatic parameters and its variability and trends have great influences on environmental and socioeconomic development. We investigate the spatio-temporal variability of precipitation occurrence frequency, mean precipitation depth, PVI and total precipitation in China based on long-term precipitation series from 1961 to 2015. As China’s topography is diverse and precipitation is affected by topography strongly, ANUSPLIN can model the effect of topography on precipitation effectively is adopted to generate the precipitation interpolation surface. Mann–Kendall trend analysis and simple linear regression was adopted to examine long-term trend for these indicators. The results indicate ANUSPLIN precipitation surface is reliable and the precipitation variation show different regional and seasonal trend. For example, there is a sporadic with decreasing frequency precipitation trend in spring and a uniform with increasing frequency trend in summer in Yangtze Plain, which may affect spring ploughing and alteration of flood risk for this main rice-production areas of China. In north-western China, there is a uniform with increasing precipitation frequency and intensity trend, which is beneficial for this arid region. Our study could be helpful for other counties with similar climate types.
Open Access
Are diverse societies less cohesive? Testing contact and mediated contact theories
(Public Library of Science, 2018) McKenna, Sarah; Lee, Eunro; Klik, Kathleen; Markus, Andrew Barry; Hewstone, Miles; Reynolds, Kate
Previous research has demonstrated that there is a negative relationship between ethnic diversity in a local community and social cohesion. Often the way social cohesion is assessed, though, varies across studies and only some aspects of the construct are included (e.g., trust). The current research explores the relationship between diversity and social cohesion across a number of indicators of social cohesion including neighbourhood social capital, safety, belonging, generalized trust, and volunteering. Furthermore, social psychological theories concerning the role of positive contact and its impact on feelings of threat are investigated. Using a sample of 1070 third generation ‘majority’ Australians and structural equation modelling (SEM), findings suggest ethnic diversity is related to positive intergroup contact, and that contact showed beneficial impacts for some indicators of social cohesion both directly and indirectly through reducing perceived threat. When interethnic contact and perceived threat are included in the model there is no direct negative effect between diversity and social cohesion. The theoretical implications of these findings are outlined including the importance of facilitating opportunities for positive contact in diverse communities.
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The SAMI Galaxy Survey: First detection of a transition in spin orientation with respect to cosmic filaments in the stellar kinematics of galaxies
(Oxford University Press, 2020) Welker, Charlotte; Bland-Hawthorn, Jonathan; van de Sande, Jesse; Lagos, Claudia; Elahi, P.; Obreschkow, Danail; Bryant, J.; Pichon, C.; Cortese, L.; Richards, Samuel N.; Medling, Anne
We present the first detection of mass-dependent galactic spin alignments with local cosmic filaments with >2σ confidence using IFS kinematics. The 3D network of cosmic filaments is reconstructed on Mpc scales across GAlaxy and Mass Assembly fields using the cosmic web extractor DISPERSE. We assign field galaxies from the SAMI survey to their nearest filament segment in 3D and estimate the degree of alignment between SAMI galaxies' kinematic spin axis and their nearest filament in projection. Low-mass galaxies align their spin with their nearest filament while higher mass counterparts are more likely to display an orthogonal orientation. The stellar transition mass from the first trend to the second is bracketed between 1010.4, 1010.9 M⊙, with hints of an increase with filament scale. Consistent signals are found in the Horizon-AGN cosmological hydrodynamic simulation. This supports a scenario of early angular momentum build-up in vorticity rich quadrants around filaments at low stellar mass followed by progressive flip of spins orthogonal to the cosmic filaments through mergers at high stellar mass. Conversely, we show that dark matter only simulations post-processed with a semi-analytical model treatment of galaxy formation struggles to reproduce this alignment signal. This suggests that gas physics is key in enhancing the galaxy-filament alignment.
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Star Cluster Ages in the Gaia Era
(American Astronomical Society, 2018) Choi, Jieun; Conroy, Charlie; Ting, Yuan-Sen; Cargile, Phillip A; Dotter, Aaron; Johnson, Benjamin D
We use the framework developed as part of the MESA Isochrones and Stellar Tracks (MIST) project to assess the utility of several types of observables in jointly measuring the age and 1D stellar model parameters in star clusters. We begin with a pedagogical overview summarizing the effects of stellar model parameters, such as the helium abundance, mass-loss efficiency, and mixing-length parameter, on observational diagnostics such as the color–magnitude diagram, mass–radius relation, and surface abundances, among others. We find that these parameters and the stellar age influence observables in qualitatively distinctive, degeneracy-breaking ways. To assess the current state of affairs, we use the recent Gaia Data Release 2 (DR2) along with data from the literature to investigate three well-studied old open clusters—NGC 6819, M67, NGC 6791—as case studies. Although there is no obvious tension between the existing observations and the MIST models for NGC 6819, there are interesting discrepancies in the cases of M67 and NGC 6791. At this time, parallax zero-point uncertainties in Gaia DR2 remain one of the limiting factors in the analysis of these clusters. With a combination of exquisite photometry, parallax distances, and cluster memberships from Gaia at the end of its mission, we anticipate precise and accurate ages for these and other star clusters in the Galaxy.
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Outer Space
(Routledge, 2023) Steer, Cassandra; Williams, Paul D.; McDonald, Matt
In this chapter, students will learn about the importance of outer space as a strategic domain, for national and international security. Space has become a security domain of equal importance alongside land, sea, air, and cyberspace, because space-based technologies support military activities on Earth and have become so critical to military operations that it has become a contested strategic domain. But outer space is also a domain which forms part of our environmental, economic, and human security. This chapter examines the ways in which we are dependent on space, why a potential conflict extending into space would seriously impact us all, efforts to prevent a conflict and restrain the weaponization of space, as well as the disruptive importance of commercial actors which have now become integral to space security.
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Redshift distributions of galaxies in the Dark Energy Survey Science Verification shear catalogue and implications for weak lensing
(American Physical Society, 2016) Bonnett, C; Troxel, M. A.; Hartley, W.; Amara, A.; Leistedt, B.; Becker, M. R.; Bernstein, G. M.; Bridle, S. L.; Bruderer, C.; Busha, M. T.; Carrasco Kind, M; Childress, Michael; Lidman, Christopher
We present photometric redshift estimates for galaxies used in the weak lensing analysis of the Dark Energy Survey Science Verification (DES SV) data. Four model- or machine learning-based photometric redshift methods—annz2, bpz calibrated against BCC-Ufig simulations, skynet, and tpz—are analyzed. For training, calibration, and testing of these methods, we construct a catalogue of spectroscopically confirmed galaxies matched against DES SV data. The performance of the methods is evaluated against the matched spectroscopic catalogue, focusing on metrics relevant for weak lensing analyses, with additional validation against COSMOS photo-z’s. From the galaxies in the DES SV shear catalogue, which have mean redshift 0.72±0.01 over the range 0.3
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Measuring Radial Orbit Migration in the Galactic Disk
(American Astronomical Society, 2018) Frankel, Neige; Rix, Hans-Walter; Ting, Yuan-Sen; Ness, Melissa K.; Hogg, David W.
We develop and apply a model to quantify the global efficiency of radial orbit migration among stars in the Milky Way disk. This model parameterizes the possible star formation and enrichment histories and radial birth profiles, and combines them with a migration model that relates present-day orbital radii to birth radii through a Gaussian probability, broadening with age τ as . Guided by observations, we assume that stars are born with an initially tight age-metallicity relation at given radius, which becomes subsequently scrambled by radial orbit migration, thereby providing a direct observational constraint on radial orbit migration strength . We fit this model with Markov Chain Monte Carlo sampling of the observed age-metallicity distribution of low-α red clump stars with Galactocentric radii between 5 and 14 kpc from APOGEE DR12, sidestepping the complex spatial selection function and accounting for the considerable age uncertainties. This simple model reproduces the observed data well, and we find a global (in radius and time) radial orbit migration efficiency in the Milky Way of = 3.6 ± 0.1 kpc when marginalizing over all other aspects of the model. This shows that radial orbit migration in the Milky Way's main disk is indeed rather strong, in line with theoretical expectations: stars migrate by about a half-mass radius over the age of the disk. The model finds the Sun's birth radius at ∼5.2 kpc. If such strong radial orbit migration is typical, this mechanism indeed plays an important role in setting the structural regularity of disk galaxies.
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The first sample of spectroscopically confirmed ultra-compact massive galaxies in the Kilo Degree Survey
(Oxford University Press on behalf of the Royal Astronomical Society, 2018) Tortora, Crescenzo; Napolitano, Nicola R; Spavone, Marilena; La Barbera, F.; D'Ago, Giuseppe; Spiniello, Chiara; Kuijken, Konrad; Roy, Nivya; Raj, M. A.; Cavuoti, Stefano; Lidman, Christopher; Wolf, Christian
We present results from an ongoing investigation using the Kilo Degree Survey (KiDS) on the VLT Survey Telescope (VST) to provide a census of ultra-compact massive galaxies (UCMGs), defined as galaxies with stellar masses M* > 8 × 1010M⊙ and effective radii Re < 1.5 kpc. UCMGs, which are expected to have undergone very few merger events, provide a unique view on the accretion history of the most massive galaxies in the Universe. Over an effective sky area of nearly 330 deg2, we select UCMG candidates from KiDS multicolour images, which provide high quality structural parameters, photometric redshifts, and stellar masses. Our sample of ~1000 photometrically selected UCMGs at z < 0.5 represents the largest sample of UCMG candidates assembled to date over the largest sky area. In this paper, we present the first effort to obtain their redshifts using different facilities, starting with first results for 28 candidates with redshifts z < 0.5, obtained at NTT and TNG telescopes.We confirmed, as bona fide UCMGs, 19 out of the 28 candidates with new redshifts. A further 46 UCMG candidates are confirmed with literature spectroscopic redshifts (35 at z < 0.5), bringing the final cumulative sample of spectroscopically confirmed lower-z UCMGs to 54 galaxies, which is the largest sample at redshifts below 0.5. We use these spectroscopic redshifts to quantify systematic errors in our photometric selection, and use these to correct our UCMG number counts. We finally compare the results to independent data sets and simulations.
Open Access
Oligo-Miocene radiation within South-west Pacific arc terranes underpinned repeated upstream continental dispersals in pigeons (Columbiformes)
(Linnean Society of London, 2023) Oliver, Paul M.; Hugall, Andrew F.; Prasetya, Audrey; Slavenko, Alex; Zahirovic, Sabin
Upstream colonizations from islands to continents have played an important role in two major global bird radiations: the oscine passerines and the pigeons. Here, we investigate insular diversification and upstream dispersal dynamics of pigeons (Columbiformes) within the Indo-Australian Archipelago using a supermatrix fossil-calibrated phylogeny and model-based biogeographical analyses. These analyses show that the islands of Melanesia, now centred on New Guinea and considered separately from Australia, have been a centre of pigeon diversification since the Eocene-Oligocene transition (~34 Mya). Geological reconstructions are concordant in suggesting that arc terranes and continental ribbon fragments that underpin the contemporary Melanesian region might have formed extensive archipelagos for much of the Oligocene and Miocene. These islands are also inferred to have functioned as a net source of pigeon lineages for Asia and especially Australia. Arboreal fruit-eating pigeons have colonized nearby continents on multiple occasions yet show little evidence of subsequent radiation. Insular terrestrial pigeons have been largely unable to colonize Asia, and a single Miocene colonization of Australia preceded an endemic radiation. Upstream dispersal may well be a frequent process in the history of the Indo-Australian Archipelago and surrounds, however ecological and environmental factors likely place strong constraints on its success and evolutionary outcomes.

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